1. (10 marks) Our goal is to show that I_/+oo d3k ez'k-r _ emr (1) _ _oo (27r)3 k2 +m2 471'?" ' where the last term is the Yukawa potential. (a) Express the integral I in spherical coordinates. Using it = cos 0, Where 6 is the angle between r and k, show that 1 00 2 1 eikru I = . 2 (271')2/0 dk k [ld'u k2+m2 () (b) Show that Eq. (2) leads to 1 196\"" I = . i(27r)2r /_oo dk k2 +m2 (3)